It is well documented that body mass index (BMI) — a ratio of height and weight — is not the best measure of a person’s obesity, physical fitness or good health. But coming up with another quick-calculation metric to replace BMI has proven difficult. Now, research published in Obesity suggests an option: the body-adiposity index, which is a ratio of hip circumference and height.

To develop the body fat index, Richard Bergman, of the University of Southern California, Los Angeles, and colleagues analyzed information from about 1,700 Mexican-Americans. They sought the characteristics — such as gender, age, height, weight, hip circumference or some combination of these traits — that best correlated with body fat as measured by dual-energy X-ray absorptiometry.

The researchers found that hip circumference and height were strongly linked with body fat. From these traits, the researchers developed an equation for the body adiposity index:

Hip circumference / (Height x √Height) – 18

(Like I said, you might need a calculator.)

The researchers validated their equation in a second study population of about 220 African Americans, but more work is needed to determine whether the index works also for whites.

The new index might avoid certain problems with BMI, the study authors said, like wrongly classifying fit, muscular people as obese, and it might also identify some cases of overweight that would otherwise be overlooked. But other experts say the body-adiposity index isn’t without its own pitfalls — for instance, hip measurements aren’t always easily obtained, especially on obese people.

Another limitation of the formula is that it doesn’t take into account belly fat (or waist circumference), which has been linked to heart disease, Type 2 diabetes, high cholesterol and risk of death — independent of BMI.